Add processing job runner

[oreilles]

No description provided.

[vvmruder]

@oreilles currently the exporter is broken with:
docker run --rm -ti --entrypoint /opt/qgis-server-light/venv/bin/python3 docker.io/local/opengisch/qgis-server-light:latest -m qgis_server_light.exporter.cli export-processes

I get:

xsdata.exceptions.XmlContextError: Error on Parameter::type: Xml Element does not support typing `ProcessingParameterType`

Which is due to not supported typing on de/serialisation. I think we need to revise the interface classes a bit.

[oreilles]

Fixed. typing.Literal was not compatible, replaced with str. set[str] wasn't compatible, replaced with list[str].